Releasable permanent magnet holding device



April 1942- s. N. LEVESQUE 2,280,437

RELEASABLE PERMANENT MAGNET HOLDING DEVICE Fi-led Nov. 2, 1939 Witness:M]

Patented Apr. 21, 1942 George N. Levesque, Providence, R. I., assignorto Brown and Sharpe Manufacturing Company,

a corporation of Rhode Island Application November 2, 1939, Serial No.302,569 2 Claims, (Cl. 175-367) The present invention relates toimprovements in releasable permanent magnet holding devices, and moreparticularly to a holding device of the general description whichincludes a magnetic holding member having magnetic conductors and apermanent magnet associated therewith, and means for controlling theflow of magnetic flux in a magnetic holding circuit including themagnetic conductors to hold or to release any part which may bemagnetically attracted to the holding member. l

The invention is herein disclosed as embodied in a magnetic base foradlal test indicator which is adapted 'ior use on machine tools. It isto be understood, however, that the invention is not limited in itsapplication to a magnetic base of this description, but is equallyapplicable in any instance where it is feasible and desirable to secureone part to another by magnetic attraction as, for example, in themanufacture of nonelectric magnetic chucks.

It is a principal object oi the present invention to provide a novel andimproved releasable permanent magnet holding device of this generaldescription which is simple and compact in its construction, and is alsomost emciently arranged for controlling the d p s tion of the magneticlines of flux to strongly hold and to release magnetically attractedparts.

' With this and other objects in view as may hereinafter appean-afeature of applicant's invention consists in the provision oi a'magnetic holding device including a magnet preferably, but notnecessarily, cylindrical in cross-section and having the magnetic polesthereof disposed transversely oi its longitudinal axis, and magneticconductors arranged to cooperate with the magnet to control the flow ofmagnetic lines of flux to establish a magnetic holding circuit, or torender the same. ineiiective as desired.

Other features of applicant's invention consist in the specificconstruction and arrangement oi the magnetic holding assembly includingthe parts above described, in which the portions of the magneticconductors contacting with the magnet, take the form oi substantiallysemicylindrical bearing surfaces separated by nonis shunted through eachof the conductors directly from one pole oi the magnet to the other.

The several features of the invention consist also in the devices,combinations and arrangement of parts hereinafterdescribed and claimed,which together with the advantages to be obtained thereby will bereadily understood by one skilled in the art from the followingdescription taken in connection with the accompanying drawing, in whichFig.1 is a perspective view of a dial test indicator with a magneticbase embodying in one form the several features oi applicants invention:Fig. 2 is a view in front elevation of the magnetic base with a portionof the some broken away, and the underlying parts shown on a sectionextending through the middle of the base; and Fig. 3 is a sectional viewtaken on the line 3-8 of Fig. 2.

I! which serves to support a dial indicator it of ordinary description..

The magnetic base disclosed in the drawing as embodying in a. preferrediorm the several features of applicant's invention, comprises the outershell I having roughly the shape of an inverted U. Extendingtransversely through the upper end of the outer shell 4, is asemi-cylindrical bearing surface 2! in which is received a cylindricalmagnet 22. The magnet 22 is held in .place by meansvoi a plug 24 whichis fitted into the remaining space between the two arms of the. U-shapedshell Land has formed in the upper side thereof, a cooperatingsemi-cylindrical bearing surface 20 for the cylindrical magnet 2h Theplug 24 is separated fromthe two arms of the U-shaped shell 4 by thinsheets oi nonmagnetic material 28 forming non-magnetic insulating areaswhich extend from the surface oi the cylindrical magnet 22 at oppositesides thereof, to the bottom holding suriace oi the magnetic base. Asbest shown in Figs. 2 and 3, the cylindrical magnet 22 is held in placeby means of a pin Ill screw-threaded into the bottom of the plug 24 forengagement in a transverse slot 32 formed in the middle portion of thecylindrical magnet 22. The pin 30 cooperating with the slot :2 serves toprevent endwise movement of the magnet 22, and permits rotationalmovement contacting the end of the magnet.

through a 90 angle between the designated "on" and "ofi positions, asindicated by the position of the manually operable knob 34 on one end ofthe magnet. I

The magnet 22 is magnetized in such a manner I as to cause the oppositepoles to be disposed trans- 'the on" position of the magnet, themagnetic lines of flux pass through a magnetic holding circuit extendingfrom the upper pole of the magnet, through the magnetic conductorprovided by the outer shell 4, downwardly through the arms of thisU-shaped member 4 to the face or holding surface of the base. Assumingthat the base is engaged against a magnetizable machine part, the linesof magnetic flux then pass through the said machine part, and thenceupwardly through the magnetic conductor provided by the plug 24 to thebottom or oppositely polarized side of the magnet.

While the base will ordinarily be placed with the bottom surface shownin the figures of the drawing, in contact with the machine, it maysometimes be desirable to position 'the base in such a manner that thestandard 6 will be parallel to the supporting surface of the machine.Under these conditions it has been found that the end of the baseopposite the knob 34 may be employed as a magnetic holding surface, andthat a very strong magnetic holding circuit will be maintained for thisposition of the base. The magnetic lines of force originating in themagnet will be circulated from one pole to the other through thatportion of. the machine surface Additional lines of force will passthrough the U-shaped member 4 into the surface of the machine partcontacting the rear end of the holding member,

Y comprising a rotatable cylindrical magnet having the magnetic polesdisposed transversely of the longitudinal cylindrical axis and ondiametrically opposite sides thereof, and a magnetic holding member inwhich the magnet is supported'for rotational movement comprising aU-shaped magnetic conductor forming the outer shell of the instrumentsupporting base and providing in the base of the U-shaped portionthereof a semi-circular bearing contact with the magnet, a secondmagnetic conductor located between the arms of the U, and providing asecond semi-circular bearing contact member for the magnet, non-magneticmaterial separating the magnetic conductors, and means for rotating themagnet in the holding member from a holding position to a releasingposition, said magnet having formed therein a transverse slot, a stoppin on the holding member engaging in said slot to prevent axialmovement of the magnet and to prevent rotational movement thereof beyondsaid magnetic holding and releasing positions, and means for rotatingthe magnet.

2. An instrument base of the class described comprising a rotatablecylindrical magnet having the magnetic poles disposed transversely ofthe longitudinal cylindrical axis and on diametrically. opposite sidesthereof, and a magnetic holding member in which the magnet is supportedfor rotational movement comprising a U-shaped magnetic conductor formingthe outer shell of the instrument supporting base and providing in thebase of the U-shaped portion thereof a semi-circular bearing contactwith the magnet, a second magnetic conductor located beand thence willpass through the block 24 to the opposite pole portion 01' the magnet22.

It will be understood that the invention is not limited to the specificembodiment shown, and that various deviations may be made therefromwithout departing from the spirit and scope of the appended claims.

What is claimed is:

1. An instrument base of the class described tween the arms of the U,and providing a second semi-circular bearing contact member for themagnet, and thin sheets of non-magnetic material separating the magneticconductors, said magnetic holding member being shaped to provide a planemagnetic holding surface comprised by said conductors and separatingnon-magnetic material extending substantially parallel to the magneticrotational axis, 'a second magnetic holdin'g surface comprised by saidconductors, separating non-magnetic material, and the magnet extendingin a plane substantially normal to the magnet rotational axis, and meansdisposed at the opposite end of the magnet from said second holdingsurface for rotating the magnet.

GEORGE N. LEVESQUE.

